Explanation:
How much mass do
flocculent spirals hide?
The above true color image of flocculent
spiral galaxy NGC 4414 was taken with the
Hubble Space Telescope
to help answer this question.
Flocculent spirals -- galaxies without well defined spiral arms --
are a quite common form of galaxy, and NGC 4414 is one of the closest.
Stars and gas near the visible edge of
spiral galaxies
orbit the center so fast that the gravity from a large amount of unseen
dark matter must be present to hold them together.
Pictured above is the photogenic center of NGC 4414.
A bright foreground star from our
Milky Way Galaxy
shines in the foreground of the image.
Although NGC 4414's center likely holds little
dark matter, understanding its matter distribution
helps calibrate the rest of the galaxy and, by deduction,
flocculent spirals in general.
By determining a precise
distance to
NGC 4414,
astronomers also hope to help calibrate the
scale to the more
distant universe.